1. Field of the Invention
The present invention relates to a gas generator for use in a restraining apparatus to be mounted in a vehicle and the like.
2. Description of Related Art
In a gas generator that uses a solid gas generating agent, a solid gas generating agent of various shapes such as granular, pellet form and disk shape is charged in a combustion chamber and combustion gas for actuation is generated by igniting and burning the gas generating agent with an ignition device. The gas generating agent is charged in the combustion chamber formed within a housing of the gas generator and retained until actuation, and it is necessary to prevent the solid gas generating agent from becoming powdered due to external vibration while being mounted in a vehicle or the like.
In a conventional gas generator, in order not to pulverize the gas generating agent, a cushion member is disposed inside the combustion chamber to absorb vibrations and alleviate impact on the gas generating agents.
FIG. 3 of U.S. Pat. No. 5,492,365 discloses a gas generator 14 in which one end of a elongated housing 50 is closed by an end wall 54, and a squib 170 fixed to a closure cap 56 is attached to an opening on the opposite end. A gas generating material body 60 arranged in the combustion chamber 64 is retained with a pad 122 placed at the end wall 54. Since the pad 122 has approximately the same cross section shape as the cross section shape of the combustion chamber 64, the operation of disposing the pad 122 is easy.
Nevertheless, if the cushion member is larger than the opening of the combustion chamber, the operation of disposing the cushion member is not easy.
For example, in a gas generator 10 shown in FIG. 1 of JP-A No. 2010-000892, a second cup member 41 defining a second combustion chamber 35 has an opening 41a whose inner diameter is considerably smaller than the inner diameter of a bottom portion 41b where the cushion member is to be disposed. In this case, it is difficult to place a cushion member of a size capable of covering the bottom portion 41b from the opening 41a. 
A disk-shaped material made of plastic foam or rubber is used as the cushion member, but when giving consideration to the workability upon disposing the cushion member on the bottom, the cushion member desirably possesses a certain level of shape-retention property (strength of a level capable of maintaining a given shape). However, in the foregoing case, it is more difficult to place the cushion member through a small opening 41a. Although a disk-shaped cushion member can be placed with folding it in two, here, the operation of unfolding the inserted cushion member and positioning it to match the shape of the bottom portion 41b becomes complicated. In addition, it is impossible to completely eliminate the possibility that the small pieces, which are produced when the cushion member and the second cup member 41 come in contact, cause unanticipated problems in the manufacture process or product quality.